chore: setup TypeScript 6 and pnpm with mise

- Add mise.toml with pnpm latest
- Create root workspace with pnpm-workspace.yaml
- Upgrade TypeScript from 5.9.3 to 6.0.3 in apps/web
- Add vite-env.d.ts for CSS module type declarations
- Switch from npm to pnpm package management

package.json

@@ -0,0 +1,11 @@
+{
+  "name": "md-hub-secure",
+  "version": "1.0.0",
+  "private": true,
+  "packageManager": "pnpm@10.10.0",
+  "scripts": {
+    "dev": "pnpm --filter web dev",
+    "build": "pnpm --filter web build",
+    "typecheck": "pnpm --filter web typecheck"
+  }
+}